Conventionally, a voice recognition technique for recognizing words spoken by a speaker from a voice signal acquired by collecting the voice of the speaker's voice has been used in user interfaces. When using a device in which a user interface using such a voice recognition technique is employed, a user who wishes to perform a desired operation is requested to utter a keyword that has been associated with the operation in advance. Therefore, if the user does not remember the keyword for performing the operation correctly, a situation occurs in which, although the user utters an incorrect keyword repeatedly, the user interface is unable to recognize the keyword for the operation and, as a consequence, the operation is not performed.
In contrast, techniques of performing voice recognition based on a voice uttered repeatedly have been proposed (see, for example, Japanese Laid-open Patent Publication No. 2007-248529).